Asthma treatments, especially inhaled corticosteroids, are less likely to work for older patients, a new study suggests.

Researchers looked at 1,200 patients with mild-to-moderate asthma, and found that treatment failure occurred in about 17 percent of those aged 30 and older, compared with about 10 percent of those younger than 30.

Lower lung function and having asthma for a longer time were associated with a higher risk of treatment failure.

When the researchers focused on specific therapies, they found that treatment failure increased consistently for every year above age 30 among patients who used inhaled corticosteroids.

Patients aged 30 and older who used inhaled corticosteroids, either alone or in combination with other therapies, were more than twice as likely to have treatment failure than those younger than 30, the investigators found.

Men and women had similar rates of treatment failure, according to the study published online June 12 in the American Journal of Respiratory and Critical Care Medicine.

The finding that older asthma patients are at increased risk for treatment failure "may involve not only biological mechanisms, such as differences in the type of airway inflammation in older patients, but may also involve socioeconomic, geographic or treatment adherence differences between older and younger patients," researcher Dr. Ryan Dunn, of National Jewish Health in Denver, said in a journal news release.

"Further research is needed to elucidate the causes underlying our observations and to examine whether older patients might benefit from a unique treatment approach," Dunn added.